Engine size for a 55 - 60 ft NB

[nb Innisfree]

The first engine in Innisfree (60') was 2.45 litres and 33bhp @ max 2000 rpm, 100 ft pounds at approx 1500 - 1600 rpm. It had a really well matched Crowther prop which allowed 2,950rpm, but when the large alternator was on full output only about 2700rpm was achievable, so in that case 33bhp was a tad too low. 2nd engine was a LPWS4, 40 BHP @ 300rpm which was more than enough. 

[Alan de Enfield]

2 minutes ago, nb Innisfree said:

40 BHP @ 300rpm which was more than enough. 

 

???

 

Nothing another "0" wouldn't fix.

 

(NO - not 400hp at 300rpm)

Edited August 17, 2019 by Alan de Enfield

[nb Innisfree]

7 minutes ago, nb Innisfree said:

The first engine in Innisfree (60') was 2.45 litres and 33bhp @ max 2000 rpm, 100 ft pounds at approx 1500 - 1600 rpm. It had a really well matched Crowther prop which allowed 2,950rpm, but when the large alternator was on full output only about 2700rpm was achievable, so in that case 33bhp was a tad too low. 2nd engine was a LPWS4, 40 BHP @ 3000rpm which was more than enough. 

Crowther reckoned the 1st prop absorbed about 25bhp at a shaft speed of 2000rpm.

4 minutes ago, Alan de Enfield said:

 

???

 

Nothing another "0" wouldn't fix.

 

(NO - not 400hp at 300rpm)

Heh heh, 400 @ 30rpm would do it ?

Edited August 17, 2019 by nb Innisfree

[MtB]

 

Bear in mind when cogitating whether 38hp is enough or 43 hp is necessary, that back in the day one horse was enough to power a 40 ton boat. 

 

And just to stir the pot a little further, one horse can deliver a peak power of 3HP, if my memory serves correctly

 

 

[OldGoat]

4 hours ago, blackrose said:

 

Except when raw water cooling sucks weed and other crap in and gets blocked. Seems to happen to my neighbour every time he goes out and he's always having to clear the intake to stop the engine cooking. Also raw water cooling has to be winterised. In comparison keel cooling is virtually maintenance free. Change the antifreeze every 5 years. I'm not sure what the "tin resonator" comment is all about? If it's properly sized for the engine then keel cooling wins hands down every time on a canal boat.

As with many things - good design helps. I've seen raw water intakes which are  an 1 1/4" tube with no mud box or even a filter.

 

Mine is a girt big 6" x 6" with a mud trap and a Vetus filter on the engine side. Even when The Management managed to fill the former with fallen leaves (? why is the engine smoking a bit....) there was still enough flow to cool the engine and exhaust stack.

There's very little fresh water in the system when at rest and plentof rogom for any ice (never had any) to expand. Easy enough to add some anti freeze via the filter if you're worried.... (Igave that up years ago)

Edited August 17, 2019 by OldGoat

[cuthound]

2 hours ago, Mike the Boilerman said:

 

Bear in mind when cogitating whether 38hp is enough or 43 hp is necessary, that back in the day one horse was enough to power a 40 ton boat. 

 

And just to stir the pot a little further, one horse can deliver a peak power of 3HP, if my memory serves correctly

 

 

 

Ah but did they have a flat torque curve? ?

[Tony Brooks]

1 minute ago, cuthound said:

 

Ah but did they have a flat torque curve? ?

I suspect its a bit like an electric motor - maximum pull (torque) at zero speed (revs).

[nebulae]

We had indirect cooling with a 42hp Isuzu. We had indirect raw water cooling ,as the Isuzu replaced an air cooled Lister,so we had no skin tanks. Over10years,we had no problems. With raw water cooling the exhaust was very quiet. The Isuzu with indirect raw water cooling was normaly supplied for sea and river boats and had a P.R.M 120 as standard. We were advised to upgrade to a P.R.M. 150 for canal use and I think this was good advice. This engine gave 1.6 litres per hour overall. The ocasional thrash on deep open water was most impressive pushing up a bow wave. However,the max speed on G.P.S. was just under 6 knots.(On a 50ft boat). At this speed,the engine/boat combination had nothing more to give and the fuel consumpion went through the roof.

[nbfiresprite]

To add to my long lasting batteries, Jabsco water pumps. I now have to add my PRM 120 gearbox to the list which has been used mostly on rivers plus two years potting around Poole Harbour moving a 48ft narrowboat around for the last 20 years.

[nicknorman]

Just to mention that propelling the boat isn't the only issue. There is electrical generation too! These days engines have large alternators, eg 175A (which is around 2kw). And maybe a Travelpower (3.5kw). They also have the pulley ratios to allow these alternators to produce this sort of output just off idle.

 

If we have just set out, the domestic alternator is giving maybe 120A. If we put the Travelpower on for the tumble drier (2kw) that is a pretty big load and our Beta 43 noticeably struggles to get the revs up when put in gear.

 

So if you have big alternators, the ability of the engine to produce high torque at low rpm is a consideration. The smaller Beta probably couldn’t do that and perhaps that is why Beta don’t offer a Travelpower option for them.

 

We went for the Beta 43 for this reason. I’ve never had it over 2200 rpm sustained (2700 is max rpm) and mostly it runs at 1300. On the rivers recently, we have been running it at 1800 and that gives an impressive bow wave! The smaller Beta would have been quite adequate for propelling the boat, but not for generating lots of electrical power at low rpm.

Edited August 18, 2019 by nicknorman

[Cheshire cat]

Oh please! We've got a Beta 33 connected to a  150 and it is fine despite my concerns. Unless you are boating full time with the tumbledrier on the go it's not that big a problem

 

[DandV]

13 hours ago, nicknorman said:

Just to mention that propelling the boat isn't the only issue. There is electrical generation too! These days engines have large alternators, eg 175A (which is around 2kw). And maybe a Travelpower (3.5kw). They also have the pulley ratios to allow these alternators to produce this sort of output just off idle.

 

If we have just set out, the domestic alternator is giving maybe 120A. If we put the Travelpower on for the tumble drier (2kw) that is a pretty big load and our Beta 43 noticeably struggles to get the revs up when put in gear.

 

So if you have big alternators, the ability of the engine to produce high torque at low rpm is a consideration. The smaller Beta probably couldn’t do that and perhaps that is why Beta don’t offer a Travelpower option for them.

 

We went for the Beta 43 for this reason. I’ve never had it over 2200 rpm sustained (2700 is max rpm) and mostly it runs at 1300. On the rivers recently, we have been running it at 1800 and that gives an impressive bow wave! The smaller Beta would have been quite adequate for propelling the boat, but not for generating lots of electrical power at low rpm.

Or you could have a smaller engine, no travelpower, but instead have a cratch and cover to air dry your clothes even when it is raining, saving the planet instead.

[nicknorman]

30 minutes ago, DandV said:

Or you could have a smaller engine, no travelpower, but instead have a cratch and cover to air dry your clothes even when it is raining, saving the planet instead.

True. Even better, we could fit the boat with solar, dump the engine and have sails for when travelling down wind, and a horse for when upwind. We would wash in canal water and use candles or an oil lamp for illumination.

 

But personally I don’t want to live in the 18th century!

 

Actually on a slightly serious note, there is a big difference between tumble dried clothes and air dried clothes. The latter dry hard. Also when air drying, clothes tend to pick up dust and pollen. Not an issue for me, but Jeff has bad hay fever and asthma and air dried clothes are a no-no for him.

[doratheexplorer]

On 17/08/2019 at 14:20, Mike the Boilerman said:

 

Bear in mind when cogitating whether 38hp is enough or 43 hp is necessary, that back in the day one horse was enough to power a 40 ton boat. 

 

And just to stir the pot a little further, one horse can deliver a peak power of 3HP, if my memory serves correctly

 

 

But the horse wasn't swimming in the canal

[PaulG]

I manage perfectly well with a Lister LPWS3 (27hp) in 55 footer, mostly on rivers.
Personally I don't think you'd notice the difference between 38 and 43 hp.
You'd rarely need to run the 38hp version flat out, so the extra 5hp would rarely get used.

[DandV]

11 hours ago, PaulG said:

I manage perfectly well with a Lister LPWS3 (27hp) in 55 footer, mostly on rivers.
Personally I don't think you'd notice the difference between 38 and 43 hp.
You'd rarely need to run the 38hp version flat out, so the extra 5hp would rarely get used.

The Beta 35 is rated at 2800rpm (or is it 2700?) whereas the 38 is rated at 3000rpm. So basically the same

The PRM 120 gearbox is a 2:1 ratio

Once the propshaft was spinning above 1100 rpm (engine at 2200rpm) more and  more things and panels on the boat found their resonant frequency and rattled furiously. No longer peacefully cruising. So I think the maximum bearable cruising horsepower would be more like 30hp with that engine gearbox combination. A bit in hand though for a burst to get out of trouble.